2. "Stellar-Mass, Intermediate-Mass, and Supermassive Black Holes" Kyoto International Community House, Kyoto, Japan October 28 - 31, 2003 "Stellar-Mass, Intermediate-Mass, and Supermassive Black Holes" Kyoto International Community House, Kyoto, Japan October 28 - 31, 2003 "Stellar-Mass, Intermediate-Mass, and Supermassive Black Holes" "Stellar-Mass, Intermediate-Mass, and Supermassive Black Holes" Direct imaging of a super massive black hole, SgrA* M.Miyoshi, Pepe Ishitsuka, S. Kameno (NAOJ), Z. Shen (Shanghai Astronomical Obs.) ＆ S. Horiuchi (SKA) Imaging the vicinity of black hole is one of the ultimate goals of VLBI astronomy. SgrA*, the closest super massive black hole, located at our Galactic center is the leading candidate for such observations. Because of the apparent Schwarzschild radius is estimated to be larger than 6- micro arc seconds from the mass (2.6-3.7*10^6 solar mass) and the distance (8 kpc), the corresponding shadow of black hole is 30 micro arc seconds in diameter and because mm and sub-mm VLBI will soon obtain the sufficient spatial resolutions for the imaging. Recent detections of the rapid flaring from a few hours to 30 min at mm-wave, infrared, and x-ray emissions mean that the structure of the black hole system of SgrA* will also change rapidly. One of VLBA observations at 43GHz really shows such rapid changes of structure of SgrA* occur. We also show performance of a supposing but realistic ground-based mm and sub-mm VLBI array for imaging the SgrA* black hole system.

3. A simulation of the appearance of black hole with accretion disk (Fukue et al 1989). Light from the other side is bended by the black hole gravity, and then we can see opposite side. At the center ‘ black hole ‘ can be seen from where no light come towards us. http://quasar.cc.osaka-kyoiku.ac.jp/~fukue/ See also Fukue’s poster in this meeting.

4. Radio Interferometer has been trying to resolve the central part of the monsters. Above all, VLBIs have the best instruments for investigating fine structures of the sources.

5. The nucleus of M87 ( VLA,VLBA ） This is one of the highest resolution VLBI maps. But, the true face of central massive black hole cannot be seen. As you already saw at Hirabayashi’s talk

6. So we must check. How small are the black holes? ～５ Rs Takahashi & Mineshige (2003) See also Takahashi’s poster in this meeting.

7. Shadow Size of Black Holes

8. If you want to look a black hole (shadow), ＳｇｒＡ＊ should be observed because it is the biggest.

9. Our galactic central black hole ＳｇｒＡ＊ is the most convincing black hole candidate.

10. SgrA* is now the best convincing MBH. M=3.65±0.25 × 10 6 M. Eisenhauer et al. 2003 Herrnstein et al 1999 Miyoshi et al 1995 NGC4258 is the second one. # Eckart’s talk

11. Our galactic central black hole ＳｇｒＡ＊ is not only the most convincing black hole candidate, but now also shows some activities though not so spectacular as its ’ old days (# Koyama ’ s talk).

12. Zhao et al 2003 ２３０ＧＨｚ １５，２２ＧＨｚ ＳｇｒＡ＊ Periodic Variation with 106day circle, Corresponding Flares at 230GHz

13. Our Galactic central BH ， ＳｇｒＡ＊ Rapid changes of its intensity are revealed recently. X ray flare (Td=10^4 –3×10^3sec) (Baganoff et al. 2001, Porquet et al. 2003) IR flare up for about 30 min (Genzel et al. 2003) Radio flare up at mm-wave length (Miyazaki, Tsutsumi & Tsuboi 準備中 )

14. Duration ~ Td=10^4 – 3*10^3 sec Time 我々 の 銀河中心ＢＨ ， ＳｇｒＡ＊ Short Time Flare of Ｘ ray ( Baganoff et al 01, Porquet et al 03 ) Baganoff et al 01

15. Our Galactic central BH ， ＳｇｒＡ＊ Rapid changes of its intensity are revealed recently. X ray flare (Td=10^4 –3×10^3sec) (Baganoff et al. 2001, Porquet et al. 2003) IR flare up for about 30 min (Genzel et al. 2003) Radio flare up at mm-wave length (Miyazaki, Tsutsumi & Tsuboi 準備中 )

16. 我々 の 銀河中心ＢＨ ， ＳｇｒＡ ＊ Flare at NIR about 30min. Genzel et al. 2003 (Nature today ） # Eckart’s talk

17. Our Galactic central BH ， ＳｇｒＡ＊ Rapid changes of its intensity are revealed recently. X ray flare (Td=10^4 –3×10^3sec) (Baganoff et al. 2001, Porquet et al. 2003) IR flare up for about 30 min (Genzel et al. 2003) Radio flare up at mm-wave length (Miyazaki, Tsutsumi & Tsuboi 準備中 )

18. Td=2*10^3 sec 我々 の 銀河中心ＢＨ ， ＳｇｒＡ Short Time Flare at mm-wave ( Miyazaki et al. 準備中 ) 我々 の 銀河中心ＢＨ ， ＳｇｒＡ ＊ Short Time Flare at mm-wave ( Miyazaki et al. 準備中 ) Next day With Nobeyama mm array (NMA)

19. Structural change of SgrA* (43GHz) 15min integration each （ 3mas*6mas ） Time Ｍｉｙｏｓｈｉ ｅｔ ａｌ． 準備中 Flux Density(Jy)

20. 0115UT-0700UT 3mas=24au@8kpc or 500Rs (2.6*10^6Msun) Kato,Mineshige & Shibata 03 See Kato’s poster

21. ← An example of testing performance 2) Simplification and Generalization of the reduction procedure from which the images derived. The procedure will be useful for mm-VLBI where atmospheric fluctuations often damage the data. 1)Tests of performance of the snap shot observation mode with VLBA I must do two things before publication of the results.

22. S ｇｒＡ＊ is not only the most convincing black hole candidate, but now also shows some activities, has become interesting However one nuisance remains. Scattering by surrounding plasma

23. VLBI images of the SgrA* from 5GHz to 43GHz. from Ｌｏ ｅｔ ａｌ （１９９９） The intrinsic image is blurred and broadened because of scattering effect.

24. Apparent Size of SgrA* Free from Scattering Effects by Plasma （∝ λ ＾２） At mm-, sub-mm wave length ! So we can expect observe the intrinsic image at mm-, sub-mm wave length. Ｄｏｌｌｍａｎｎ ｅｔ ａｌ． （２００１）

25. Shen et al. (200 ４ ) VLBA 86 GH ｚ １ｍａｓ SgrA* This is the result from the highest frequency VLBI.

26. SgrA* should be observed at mm to sub-mm VLBI if you want to look black hole.

27. First, Can we get the image of the black hole shadow of SgrA* with 86GHz VLBA? note. VLBA 86GHz observations of SgrA* is really important to measure the intrinsic size. See deeply the Poster of Shen et al. at this meeting.

28. Image Model Observed typical image + Black Hole Shadow (30×24μas PA=80° ） VLBA VLBA+ Huancayo+ALMA+SEST さかさＶＬＢＡ at south Here in order to estimate the performance of spatial resolutions of several arrays, ignoring scattering effects and weather conditions, but using the real sensitivities, we made clean simulations. At 86GHz ground based VLBI, the shadow of SgrA* will not be detected only because insufficient spatial resolutions.

29. Then, What kind of sub-mm VLBI array should we construct for imaging the black hole shadow of SgrA*? I made simulations with three types of arrays. ＳｇｒＡ＊ locates at δ ＝－３０ °, Observations from the southern hemisphere is preferable.

30. ２５ｍ鏡１０台 最大 ８０００ km 基線 （ 最小フリンジ間隔 ０．２ mas ＠４３ＧＨｚ ） ３００ＭＨｚ～ 86 Ｇ Ｈｚ Case 1. VLBA NOTE. VLBA antennas do not have sufficient surface accuracy to receive sub mm radio waves.

31. 2005: High site is fully operational BIMA Photo by Ota Naomi SMA ALMA OVRO SEST Huancayo virtual Case2. realistic sub mm Stations

32. ＶＬＢＡ（ VLBI Array ） Ｎｏｒｔｈ 北 南 Ｓｏｕｔｈ Case 3. Ｉｎｖｅｒｓｅｄ ＶＬＢＡ （さかさＶＬＢＡ）

33. uv coverage for SgrA* １．５ mas ＠８６Ｇ 0.56mas@230GHz 1.VLBA 2. SMA+ CARMA+Huancayo+ALMA+SEST 3. さかさＶＬＢ Ａ dirty beam for SgrA*

34. Gaussian 0.1×0.08mas, PA=80 °,f=3Jy Black Hole Shadow 30×24μas PA=80° 230GHz simulations 250μas Super resolution(20μas beam) 使用 Outer size 0.1mas from Krichbaum obs 1.VLBA 2. SMA+ CARMA+Huancayo+ALMA+SEST 3. さかさＶＬ ＢＡ Good image was obtained from ‘inversed VLBA’ as expected

35. In order to image the black hole of SgrA*, we must observe with sub-mm VLBI. We need the same scale array like VLBA, (8000km,10 Stations, same sensitivity as that of 86GHz of real VLBA) located at the southern hemisphere. model Image from simulation

36. But, How about sub-mm VLBI with small number of stations? Is it useless for investigating the black hole shadow of SgrA*? model Image from simulation

37. We can estimate the shadow size and then the BH mass with submm VLBI including only small number of stations.b Null point shifts with the size of BH shadow, namely BH mass ＢＨ ２．６ × １０＾ ６Ｍｓ Ds= ３０ μ ａ ｓ NO Black hole NO Shadow An Example of the relation of Visibility Amplitudes and Structure of S ｇｒＡ＊ （２３０ＧＨ ｚ） ＢＨ ３．７ × １０＾６ Ｍｓ Ds= ４４ μ ａｓ

38. Huancayo ＳＥＳＴ１５ｍ鏡（ＥＳ Ｏ） ＡＬＭＡ（日米欧） 1960km 800km 1520km South America Photo by Ota Naomi Virtual now Construction begins Since 1987 Old 32m communication antenna

39. In order to image Black Hole directly: 1)the first and best target should be SgrA* SgrA* has the biggest apparent size of black hole shadow (D=30-45 micro arc sec ) SgrA* shows short time flares, then we can expect to investigate the active phenomena occurring on accretion disk. 2) Sub mm VLBI ( 230GHz or higher frequency ) with like VLBA location (=10 stations & 8000km ) in southern hemisphere is needed to image clearly.

40. However, from visibility analysis with image models we can begin to investigate BH shadow even with sub- mm VLBI using only small number of stations.

41. Conclusions So We Should Start sub-mm VLBI at the Southern Hemisphere at once! SgrA* Black Hole Shadow (Falcke et al 00) Thanks !